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(1). Field of the Invention
The present invention relates generally to a system for tracking objects on the earth""s surface using global positioning system (GPS) satellites and then transmitting that position information via radio signal to a base receiver, and more particularly, a rugged, solar-powered, self-contained system utilizing GPS, cell phone control channel data transmission technology, and the Internet to deliver the object""s position to the end user.
(2). Background Information
The tracking of various cargo and other shipments by industry is becoming a highly desirable service to both customers and the shipping industry. With greater use of global computer networks, the consuming public demands greater accuracy and tracking capabilities for various products and shipments.
One example is the trucking industry, wherein drivers of vehicles periodically communicate with a home office to report the location of the vehicle and the status of the shipment. Similar systems are used for the shipping of mail and other packages, with updates to the location of the package with the carrier, as well as its estimated time of arrival, and other related information. Another industry where tracking of cargo is highly desirable is the railroad industry. The capability of tracking a particular freight car and shipment has become quite valuable to this industry.
In the prior art, there are three main systems for determining the location of a vehicle or object. First, the vehicle or shipment may be manually tracked by a person identifying the particular shipment and its location, and manually calling in that location to a home office. The trucking industry conventionally utilizes a system of this sort, but individual tracking of train cars by such a system would be unfeasible.
Other systems for tracking vehicles and shipments include LORAN and GPS. Both of these systems rely on externally transmitted radio frequency signals to calculate the location of a receiving antenna mounted on the vehicle. In LORAN systems, the calculation is based on the time difference and signals received from multiple transmitters. Because the latitude and longitude of the transmitters are known, the distance from two or more transmitters can be calculated from the time differential between the reception of the plurality of signals.
In the GPS tracking system, transmitters are positioned on orbiting satellites. GPS uses a suedo-random data stream encoded on each satellites"" carrier frequency. The receiver is synchronized with the data stream by matching an identical suedo-random data stream albeit with a time offset. The time offset between the receiver""s data stream and the data stream received from the satellite give the distance to that satellite via the speed of light that the radio signal traveled. The receiver then triangulates its position using three or more satellites and by knowing where the satellites are via their ephemeris data. GPS systems have been developed to be extremely accurate in locating and tracking a receiver on the surface of the earth.
One of the main drawbacks of prior art GPS tracking systems is the GPS unit""s dependency on power provided by the object being tracked. In the trucking industry, the units draw a sufficient amount of power that they must be connected to the electrical system of the vehicle for continuous use over a period of time. Similarly, tracking a train having a plurality of freight cars would occur by mounting the GPS receiver in the locomotive, to a source of electrical power located only therein.
Other methods for tracking or reporting the position of a railcar (and its load) have included the use of bar-codes on each car which are scanned by readers located at railyards (on other locations). This was modified by the use of Radio Frequency IDentification (RFID) tags, which respond with a unique code upon interrogation by a track-side reader. The drawbacks to both these methods include: (1) the location of a car is reported to the railroad and not to the owner of the shipment/load; and (2) the methods can only report the location of a car which moves by a reader, and therefore is not a generalized locating device.
It is therefore a general object of the present invention to provide an improved generalized tracking unit and associated tracking system.
Another object of the present invention is to provide a self-powered and self-contained tracking receiver/transmitter.
A further object is to provide a tracking receiver which will transmit a wide variety of data with a simple and small block of information.
Yet another object of the present invention is to provide a self-contained receiver/transmitter unit which may be attached to a cargo container and will automatically transmit information for long periods of time and withstand harsh environments of weather and vibrations.
These and other objects of the present invention will be apparent to those skilled in the art.
The portable self-contained tracking unit of the present invention includes an enclosure attached to a mounting plate, with a hollow interior cavity housing a GPS receiver, a microprocessor, a transmitter and rechargeable batteries. The GPS receiver will receive tracking data and the microprocessor will process the tracking data into a data packet. The transmitter transmits the data packet to a remote receiving station, for transmission to a central database. Photoelectric cells are mounted on the enclosure to provide power to the rechargeable batteries which power the components of the tracking unit. The enclosure is designed with a pair of vertically oriented side panels which are generally orthogonally oriented so that the solar panels mounted on the side panels will maintain a favorable solar incidence angle during a wide range of orientations. The transmitter is a cellular telephone with an antenna mounted within the enclosure but spaced a distance from the metal mounting plate and electrical components approximately one-quarter wavelength of the operating frequency of the transmitter. The enclosure is formed of a radio frequency and optically transparent material, so that the antenna and the solar panels may be housed within the hollow interior cavity of the enclosure. In the method of the invention, tracking data is periodically transmitted via cellular phone to a cellular service provider, thence to a data service bureau which sends the data over the Internet to the database of a central server computer. The server computer will decode the information and provide an interface for customers via web pages on the Internet.